PRTG Manual: SMTP&POP3 Round Trip Sensor

The SMTP&POP3 Round Trip sensor monitors the time it takes for an email to reach a Post Office Protocol version 3 (POP3) mailbox after being sent using Simple Mail Transfer Protocol (SMTP). It sends an email using the parent device as SMTP server and then scans a dedicated POP3 mailbox until the email comes in.

The SMTP&POP3 Round Trip sensor will delete these emails automatically from the mailbox as soon as PRTG retrieves them. Emails will only remain in the mailbox particularly if a timeout or a restart of the PRTG server occurred during sensor runtime.

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

We recommend that you add this sensor to an SMTP server device only, because the settings of this sensor type are optimized for this scenario.

Sensor Settings

On the details page of a sensor, click the Settings tab to change its settings.

Usually, a sensor connects to the IP Address or DNS Name of the parent device where you created this sensor. See the Device Settings for details. For some sensor types, you can define the monitoring target explicitly in the sensor settings. See below for details on available settings.

Enter one or more Tags, separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with round parentheses (()) or angle brackets (<>).

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. Top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Default Tags

pop3sensor, roundtrip, mailsensor

Email Settings

From

Specify the address that the sent emails will contain in the from field. Please enter a valid email address.

Enter a server name for the HELO part of the mail protocol. For some mail servers the HELO identifier must be the valid principal host domain name for the client host. See SMTP RFC 2821.

Step 1: Send Email with Parent Device as SMTP Server

In this step, you configure how PRTG sends the emails. As SMTP server, the sensor uses the IP Address/DNS Name of the device you add this sensor to.

Port

Enter the number of the port that the sensor uses to send an email via SMTP.

For non-secure connections usually port 25 is used, for SSL/TLS connections port 465 or 587. The actual setting depends on the server you connect to.

If you do not get a connection, try another port number.

Please enter an integer value. We recommend that you use the default value.

Timeout for SMTP Connection (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value defines, the sensor will cancel the request and show a corresponding error message. Please enter an integer value. The maximum value is 900 seconds (15 minutes).

SMTP Authentication Type

Define if you want to use an authentication for the SMTP connection. Choose between:

None: Do not use any authentication method.

Username/Password: Authenticate at the SMTP server via username and password.

Username

This field is only visible if you enable Username/password above. Enter a username for SMTP authentication. Please enter a string.

Password

This field is only visible if you enable Username/password above. Enter a password for SMTP authentication. Please enter a string.

Additional Text for Email Subject

The subject part of the round trip email is created automatically by PRTG. It consists of the string PRTG Roundtrip Mail:, followed by a unique GUID to correctly identify the email in the POP3 mailbox, for example, PRTG Roundtrip Mail: {5E858D9C-AC70-466A-9B2A-55630165D276}.

Use this field to place your custom text before the automatically created text.

Transport-Level Security

SMTP Specific

Define the security level for the sensor connection. Choose from:

Use Transport-Level Security if available using StartTLS (default): Choose this option to try to connect to the server using TLS and StartTLS. If the server does not support this, the sensor will try to connect without encryption.

Use Transport-Level Security if available: Choose this option to try to connect to the server using TLS. If the server does not support this, the sensor will try to connect without encryption.

Enforce Transport-Level Security using StartTLS: Choose this option to try connecting to the server using TLS and StartTLS. If the server does not support this, the sensor will show a Downstatus.

Enforce Transport-Level Security: Choose this option to try to connect to the server using TLS. If the server does not support this, the sensor will show a Downstatus.

If the sensor connects to a server via StartTLS, the connection is established unencrypted first. After the connection is established, the sensor sends a certain command (StartTLS) over the unencrypted connection to negotiate a secure connection via the SSL/TLS protocol.

If the sensor uses TLS without StartTLS, the negotiation of a secure connection happens immediately (implicitly) so that no commands are sent in unencrypted plain text. If there is no secure connection possible, no communication will take place.

Step 2: Check a POP3 Mailbox Until Email Arrives

In this step, you configure how to receive the sent emails.

IP Address/DNS Name

Specify the POP3 server. Enter a valid IP address or DNS name.

Port

Specify the port that the sensor uses for the POP3 connection.

For non-secure connections usually port 110 is used, for SSL/TLS connections port 995. The actual setting depends on the server you are connecting to.

If you do not get a connection, please try another port number.

Please enter an integer value. We recommend that you use the default value.

Connection Interval (Sec.)

Enter the number of seconds the sensor will wait between two connections to the IMAP server. PRTG will continuously check the mailbox in this interval until the email arrives. Please enter an integer value.

Maximum Trip Time (Sec.)

Enter the number of seconds an email may take to arrive in the POP3 mailbox. PRTG will continuously check the mailbox in the interval that you specify above until the email arrives. If it does not arrive within the maximum trip time, the sensor will trigger an error message. Please enter an integer value.

POP3 Authentication Type

Select the kind of authentication for the POP3 connection. Choose from:

Without Login: Monitor the connection to the POP3 server only.

Username and Password: Log in to the POP3 server with username and password (simple login, non-secure).

128-bit MD5 hash value (APOP): Send the password in an encrypted form using APOP. This option must be supported by the POP3 server you connect to.

Username

This field is only visible if you enable an option with login above. Enter a username for POP3 authentication. Please enter a string.

Password

This field is only visible if you enable an option with login above. Enter a username for POP3 authentication. Please enter a string.

Transport-Level Security

POP3 Specific

Define the security level for the sensor connection. Choose from:

Use Transport-Level Security if available using StartTLS (default): Choose this option to try to connect to the server using TLS and StartTLS. If the server does not support this, the sensor will try to connect without encryption.

Use Transport-Level Security if available: Choose this option to try to connect to the server using TLS. If the server does not support this, the sensor will try to connect without encryption.

Enforce Transport-Level Security using StartTLS: Choose this option to try connecting to the server using TLS and StartTLS. If the server does not support this, the sensor will show a Downstatus.

Enforce Transport-Level Security: Choose this option to try to connect to the server using TLS. If the server does not support this, the sensor will show a Downstatus.

If the sensor connects to a server via StartTLS, the connection is established unencrypted first. After the connection is established, the sensor sends a certain command (StartTLS) over the unencrypted connection to negotiate a secure connection via the SSL/TLS protocol.

If the sensor uses TLS without StartTLS, the negotiation of a secure connection happens immediately (implicitly) so that no commands are sent in unencrypted plain text. If there is no secure connection possible, no communication will take place.

Debug Options

Sensor Result

Define what PRTG will do with the sensor results. Choose between:

Discard sensor result: Do not store the sensor result.

Write sensor result to disk (Filename: Result of Sensor [ID].txt): Store the last result received from the sensor to the Logs (Sensors) directory in the PRTG data folder on the probe system the sensor is running on (on the Master node if in a cluster). File names: Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This is for debugging purposes. PRTG overwrites these files with each scanning interval. For more information on how to find the folder used for storage, see section Data Storage.

This option is not available when the sensor runs on the Hosted Probe of a PRTG hosted by Paessler instance.

Sensor Display

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor.

You can set another primary channel later by clicking the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

Show channels independently (default): Show an own graph for each channel.

Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This will generate an easy-to-read graph that visualizes the different components of your total traffic. This option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channel Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Root group's settings, see section Inheritance of Settings for more information. To change a setting only for this object, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that a sensor has time to reach and check a device again in case a sensor query fails. The sensor can try to re-reach and check a device several times, depending on the option you select here, before it will be set to a Downstatus. This helps you avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose from:

Set sensor to down immediately: The sensor will show an error immediately after the first failed request.

Set sensor to warning for 1 interval, then set to down (recommended): After the first failed request, the sensor will show a warning status. If the following request also fails, the sensor will show an error.

Set sensor to warning for 2 intervals, then set to down: Show an error status only after three consecutively failed requests.

Set sensor to warning for 3 intervals, then set to down: Show an error status only after four consecutively failed requests.

Set sensor to warning for 4 intervals, then set to down: Show an error status only after five consecutively failed requests.

Set sensor to warning for 5 intervals, then set to down: Show an error status only after six consecutively failed requests.

Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor to Down immediately, so the first option will not apply to these sensor types. All other options can apply.

If a sensor has defined error limits for channels, it will always show a Down status immediately, so no "wait" option will apply.

If a channel uses lookup values, it will always show a Down status immediately, so no "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

Inheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

Schedules are generally inherited. New schedules will be added to existing ones, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a maintenance window, the current sensor and all child objects will not be monitored. They will be in a Paused status instead. Choose between:

Not set (monitor continuously): No maintenance window will be set and monitoring will always be active.

Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

To terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Dependency Type

Define a dependency type. You can use dependencies to pause monitoring for an object depending on the status of another object. You can choose from:

Use parent: Use the dependency type of the parent device.

Select a sensor: Use the dependency type of the parent device. Additionally, pause the current sensor if another specific sensor is in a Down status or in a Paused status caused by another dependency. Select below.

Master sensor for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of its parent device: If the sensor is in a Down status, the device will be paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor will be paused if the parent group is paused by another dependency.

Testing your dependencies is easy! Simply select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current sensor will depend.

Dependency Delay (Sec.)

This field is only visible if you enable Select a sensor above. Define a time span in seconds for dependency delay.

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects will be additionally delayed by the defined time span. This can help avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

This setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, please define delays in the parent Device Settings or in its parent Group Settings.

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown. It contains all user groups from your setup. For each user group, you can choose from the following access rights:

Inherited: Use the access rights settings of the parent object.

None: Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.

Read: Users in this group can see the object and review its monitoring results.

Write: Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.

Full: Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groupssettings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

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